Activation of the High-Mobility Group Box 1 Protein-Receptor for Advanced Glycation End-Products Signaling Pathway in Rats During Neurogenesis After Intracerebral Hemorrhage

Abstract

500I ntracerebral hemorrhage (ICH) accounts for roughly 15% of all strokes and is associated with mortality rates approaching 50%; survivors are often left with serious disability.1 The brain responds to ICH in complex ways that involve pathophysiological responses, such as excitotoxicity, free radical damage, and inflammation. Moreover, the brain initiates remodeling processes, such as neurogenesis, angiogenesis, and synaptic plasticity, designed to restore neurological function after ICH.2-4 As part of this neurogenesis, precursor cells in the subventricular and subgranular zones of the hippocampus migrate into injured brain areas, where they differentiate into mature neurons and glia. [4][5][6] High-mobility group box 1 (HMGB1), a highly conserved nonhistone nuclear DNA-binding protein, is passively released by necrotic cells or actively secreted by macrophages, myeloid dendritic cells, and natural killer cells. 7-9Immediately after ICH, HMGB1 serves as an alarmin or damage-associated molecular signal that mediates cross-talk between damaged and healthy cells and triggers an inflammatory response.7-9 At later times after ICH, however, HMGB1 may promote neurogenesis that supports recovery of neuronal function. HMGB1 has been shown to increase neurite outgrowth in cultures and to promote neurovascular remodeling in cerebral ischemia in mice.10 However, the involvement Background and Purpose-Following intracerebral hemorrhage (ICH), high-mobility group box 1 protein (HMGB1) may promote neurogenesis that supports functional recovery. How HMGB1 regulates or participates in this process is unclear, as are the pattern recognition receptors and signaling pathways involved. Methods-ICH was induced by injection of collagenase in Sprague-Dawley rats, which were treated 3 days later with saline, with the HMGB1 inhibitor ethyl pyruvate or with FPS-ZM1, an antagonist of the receptor for advanced glycation end-products. A Sham group was treated with saline solution instead of collagenase and then treated 3 days later with saline again or with ethyl pyruvate or N-benzyl-4-chloro-N-cyclohexylbenzamide (FPS-ZM1). Expression of the following proteins was measured by Western blot, immunohistochemistry, or immunofluorescence: HMGB1, receptor for advanced glycation end-products, toll-like receptor (TLR)-2, TLR4, brain-derived neurotrophic factor, and matrix metalloproteinase-9. The number of cells positive for 5-bromo-2-deoxyuridine or doublecortin was determined by immunohistochemistry and immunofluorescence. Results-Levels of HMGB1, receptor for advanced glycation end-products, TLR4, TLR2, brain-derived neurotrophic factor, and matrix metalloproteinase-9 were significantly higher 14 days after ICH than at baseline, as were the numbers of 5-bromo-2-deoxyuridine-or doublecortin-positive cells. At the same time, HMGB1 moved from the nucleus into the cytoplasm. Administering ethyl pyruvate significantly reduced all these ICH-induced increases, except the increase in TLR4 and TLR2. Administering FPS-ZM1 reduced the ICH-induced increa...

Anti-high mobility group box-1 (HMGB1) antibody inhibits hemorrhage-induced brain injury and improved neurological deficits in rats

“…Interestingly, the administration of anti-HMGB1 neutralizing mAb has been shown to protect the BBB and to inhibit the inflammation cascade in rat models of middle cerebral artery occlusion/reperfusion-induced infarction and fluid percussion-induced traumatic brain injury111213. The recent studies also reported the increase in HMGB1 levels in peri-hematomal regions in subacute phase after ICH in rats181920, however, there was little information about the acute dynamics of HMGB1 in the core area after ICH. Moreover, whether anti-HMGB1 mAb can also provide neuroprotective effects in a rat model of ICH remains to be seen.…”

TLR2 Regulates Complement-Mediated Inflammation Induced by Blood Loss During Hemorrhage

“…However, in myocardial IR, TLR2 is not required for IL-6 (37) and may or may not be required for TNFα production (37, 38). Finally, after intracerebral hemorrhage, HMGB-1 appears to stimulate TLR2 and TLR4 and provide a beneficial neurogenesis at later time points (39). …”

Inhibiting HMGB1 Reduces Cerebral Ischemia Reperfusion Injury in Diabetic Mice

“…High mobility group box1 (HMGB1) is a highly conserved non-histone DNA-binding nuclear protein that is ubiquitously expressed in eukaryotic cells and regulates transcription [5]. HMGB1 promotes inflammatory injury [6, 7] by inducing the expression of cytokines such as IL-1β, IL-6, and inflammation-related enzyme inducible nitric oxide synthase (iNOS) [4, 8–10], which are known to play key roles in the development of brain I/R [11–14].…”